CN1344674A - Prepn of nano-carbon tube - Google Patents

Abstract

The invention relates to the preparation of carbon nanotubes. The hydrogen reduction products of hydrogen storage alloy oxides are used as catalysts, and hydrocarbons, natural gas, coal gas, liquefied gas, CO or _CO2 are catalytically cracked to prepare carbon nanotubes. The hydrogen storage alloy is oxidized in air or oxygen at 373-1073K, the oxidation product is reduced with hydrogen at 573-1073K for 10-60 minutes, and then the mixed gas of hydrocarbon and other reaction gases and carrier gas is introduced at 573-1373K. The hydrocarbon is methane or acetylene or ethylene or benzene vapor, the carrier gas is hydrogen, argon or nitrogen, the gas flow rate is 5-500 ml/hour, and the reaction time is 10-180 minutes. The invention has the advantages of simple and convenient operation, low cost and stable performance.

Description

Preparation method of carbon nanotube

The invention relates to the preparation of carbon nanotubes, in particular, the hydrogen reduction products of hydrogen storage alloy oxides are used as catalysts, and hydrocarbons or natural gas or CO or _CO2 are catalytically cracked to prepare carbon nanotubes.

Carbon nanotubes have attracted widespread attention in the scientific community due to their unique physical and chemical properties, and are expected to play an important role in the fields of gas storage, nanoelectronics, enhanced material science, and chemistry. At present, the preparation methods mainly include arc discharge method, chemical vapor deposition method and laser evaporation method. The preparation of carbon nanotubes by chemical vapor deposition has been widely used due to the advantages of simple process and low cost, among which the preparation of highly dispersed catalysts is very important. In the published or authorized patents, the catalysts for the preparation of carbon nanotubes mainly use chemical methods to disperse transition metal oxides such as NiO, CoO, CuO, etc. in alkaline earth metal oxides such as MgO, CaO, etc. or rare earth metal oxides such as _La2 O ₃ , CeO ₂ etc. (CN 1170631A); There is also a sol-gel method to disperse nano-scale transition metals into a silica template with nano-scale micropores as a catalyst for growing nanotubes (ZL 96120461.3); in continuous growth In carbon nanotubes, also can adopt Fe, the organic compound of Ni or Co as the catalyzer (CN1221048A) of reaction; In adopting alloy catalyst method, also have the Ni-Cu alloy (S. Motojima et al., Applied Physics Letters, 27(1989) 315) or Ni-Fe alloy thin film (XH Chen et al., ThinSolid Film 339(1999) 6.). The above-mentioned preparation methods have problems of cost, dispersion and yield invention to varying degrees.

The purpose of the present invention is to provide a new method for preparing carbon nanotubes, which can overcome the shortcomings of the existing preparation technology. The invention uses the hydrogen storage alloy oxide as the precursor of the catalyst to prepare the carbon nanotube, and has the advantages of low cost, good dispersibility and high yield. Such carbon nanotubes can be applied to large-scale storage and transportation of hydrogen, hydrogen sources for fuel cells, nickel-metal hydride batteries, hydrogen purification, organic hydrogenation catalysis, reinforcing materials, field emission materials, nanoprobes, etc.

The invention mainly utilizes the hydrogen reduction product of the hydrogen storage alloy oxide as the catalyst. It combines the advantages of iron or/and cobalt or nickel or/and molybdenum in the alloy with high dispersion, uniform composition, easy preparation and easy control in the hydrogen storage material. The hydrogen storage alloy powder is oxidized as the preparation of carbon nano The catalyst precursor of the tube, the precursor oxide can provide the nanoscale iron or/and cobalt or/and nickel or/and molybdenum catalytic sites required for the growth of carbon nanotubes after hydrogen reduction, and the metal catalyst is uniformly dispersed in the storage The rare earth metal or/and zirconium or/and titanium or/and magnesium oxide carrier in the hydrogen alloy component. Hydrogen storage alloy materials can be prepared by metal smelting, powder metallurgy, mechanized alloying, chemical reduction-diffusion and co-deposition chemical reduction-diffusion, etc. The hydrogen storage alloy may be a recycled hydrogen storage alloy.

The main steps of the invention are as follows: the preparation of carbon nanotubes is carried out on a fixed-bed gas continuous flow reaction device. Oxidize the hydrogen storage alloy powder with a particle size of 0.01-200 μm in air or oxygen at 373-1073K for 2-100 minutes, and place the metered hydrogen storage alloy oxidation product (accounting for 1-30% of the output of carbon nanotubes) in a fixed bed On the gas continuous flow reaction device (tube resistance furnace), hydrogen reduction at 573-1073K for 5-120 minutes, nickel or/and cobalt or/and iron or/and molybdenum in the alloy oxide is reduced to a metal state And uniformly dispersed in the rare earth metal or/and zirconium or/and titanium or/and magnesium oxide in the hydrogen storage alloy component, and becomes a catalyst for the growth of carbon nanotubes. Feed reaction gas or mixed gas with carrier gas at 573-1373K, the reaction gas is hydrocarbon, natural gas, coal gas, liquefied gas, CO or CO ₂ , the carrier gas is hydrogen, argon, helium or nitrogen . The gas flow rate is 5-500 ml/hour, the ratio of reaction gas to carrier gas in the mixed gas is 1/0.1-1/20, and the reaction time is 10-180 minutes.

The hydrogen storage alloy described in the present invention is rare earth nickel system, zirconium-based or titanium-based or rare-earth nickel-based Laves phase system AB ₂ type, titanium-nickel system or titanium-iron system AB type, magnesium-based alloy A ₂ B type or amorphous alloy Any one or more than two kinds of binary or multi-element hydrogen storage alloys; the composition of the rare earth nickel alloy in the hydrogen storage alloy is LNi _nxyz Co _x N _y M _z , L is mixed rare earth metal, La, Ce, Nd, Pr, Y, N and M are Mn, V, Cr, Al, Fe, Cu, Zn, Sn, Mo or Si respectively, 3≤n≤6, 0≤x≤2, 0≤y≤2, 0≤z≤2 ; Zirconium-based or titanium-based or rare earth nickel-based Laves phase system AB ₂ type alloy composition is KNi _abcd V _b G _c J _d , K is Zr, Ti, Hf, mixed rare earth metals, La, Ce, Nd, Pr or Y, G and J are Co, Mn, Cr, Al, Fe, Cu, Zn, Sn, Mo or Si respectively, 1.2≤a≤3.0, 0≤b≤2, 0≤c≤2, 0≤d≤2; titanium The composition of nickel-based or titanium-iron-based AB alloys is HNi _mkj Fe _k P _j , H is Zr, Hf, P is Co, Mn, V, Cr, Al, Cu, Zn, Sn, Mo or Si, 0.6≤m≤ 1.5, 0≤k≤1.5, 0≤j≤1; magnesium-based alloy A ₂ B type alloy composition is Mg _gf E _f Ni _lpq Co _p T _q , E is Ca, Zr, Ti, Hf, mischmetal, La , Ce, Nd, Pr or Y, T is Mn, V, Cr, Al, Fe, Cu, Zn, Sn, Mo or Si, 1.0≤g≤3.0, 0≤f≤1.5, 0≤p≤1.0,0 ≤q≤1.0.

The present invention combines the advantages of uniform composition, easy preparation and easy control in hydrogen storage materials and the advantages of highly dispersed metal catalysts such as iron or/and cobalt or/and nickel or/and molybdenum in the reduction products of alloy oxides; provide D- A new type of carbon nanotube preparation technology with stable performance and wide application.

Below by example the present invention will be further described:

Example 1

The LaNi ₅ smelted in an electric arc furnace was crushed to 20 μm-50 μm, and after heat treatment at 773K in the air for 20 minutes, the prepared alloy oxide catalyst sample was obtained. The preparation of carbon nanotubes is carried out on a fixed-bed gas continuous flow reaction device. Heat 150mg of the alloy oxide catalyst to 873K for 20 minutes in a hydrogen atmosphere and reduce it for 20 minutes, then pass a mixed gas of methane and argon with a flow rate of 15ml/cm ² min, stop the reaction after 30 minutes, cool down to room temperature in a nitrogen atmosphere, and collect The yield of the product, carbon nanotubes, was 2.5 g. Figure 1 is a TEM photo of the prepared carbon nanotubes.

Example 2

The LaNi _4.5 Fe _0.5 smelted in an electric arc furnace was pulverized to 20 μm-40 μm, and after heat treatment at 723K in air for 30 minutes, the prepared alloy oxide catalyst sample was obtained. The preparation of carbon nanotubes is carried out on a fixed-bed gas continuous flow reaction device. After heating 200mg of alloy oxide catalyst to 873K for 20 minutes in a hydrogen atmosphere and reducing it, pass a mixed gas of methane and argon at a flow rate of 10ml/cm ² min, the ratio of methane to argon is 1:10, and stop after 60 minutes of reaction , the temperature was lowered to room temperature in an argon atmosphere, and the product was collected. The yield of carbon nanotubes was 2.1 g.

Example 3

The ZrV _0.2 Mn _0.4 Co _0.3 Ni _1.2 alloy smelted in an electric arc furnace was crushed to 10 μm-30 μm, and then oxidized at 873K for 50 minutes in an oxygen atmosphere to obtain the prepared alloy oxide catalyst sample. Carbon nanotubes were prepared on a fixed-bed gas continuous flow reaction device. Heat 150mg of catalyst to 873K under hydrogen atmosphere, stabilize for 30 minutes, then pass through acetylene at a flow rate of 15ml/cm ² min, the ratio of acetylene to nitrogen is 1:5, stop the reaction after 120 minutes, and cool down to room temperature in nitrogen atmosphere , the product was collected, and the yield of carbon nanotubes was 1.0 g.

Example 4

The LFe _0.5 Ni _1.5 (L is mixed rare earth metal) alloy smelted in an electric arc furnace was crushed to 20 μm-40 μm, and then oxidized at 773K for 20 minutes in an oxygen atmosphere to obtain the prepared alloy oxide catalyst sample. Carbon nanotubes were prepared on a fixed-bed gas continuous flow reaction device. Raise the temperature of 120mg catalyst to 893K under the hydrogen atmosphere, stabilize it for 20 minutes, then pass the liquefied gas with a flow rate of 15ml/cm ² min, the ratio of liquefied gas and argon is 1:15, stop the reaction after 110 minutes, The temperature was lowered to room temperature, and the product was collected. The yield of carbon nanotubes was 1.0 g.

Example 5

The TiFe _0.7 Ni _0.3 alloy prepared by electric arc furnace smelting was crushed to 40 μm-60 μm, and after heat treatment at 823K in air for 40 minutes, the prepared alloy oxide catalyst sample was obtained. The preparation of carbon nanotubes is carried out on a fixed-bed gas continuous flow reaction device. Heat up 150mg of alloy oxide catalyst to 973K in a hydrogen atmosphere, after reduction for 30 minutes, pass through ethylene with a flow rate of 25ml/cm ² min, stop the reaction after 90 minutes, cool down to room temperature in _H2 atmosphere, collect the product, carbon nanometer Tube yield was 0.8 g.

Example 6

Mg and Ni powder were mixed at a molar ratio of 2:1, and then ball milled for 70 hours under an argon atmosphere to obtain the prepared Mg ₂ Ni amorphous alloy catalyst sample, and the amorphous alloy grain size was 100-200 nanometers. Carbon nanotubes were prepared on a fixed-bed gas continuous flow reaction device. Raise the temperature of 150mg catalyst to 873K in a hydrogen atmosphere. After 30 minutes of stabilization, the temperature rises to 1023K, and then benzene vapor with a flow rate of 15ml/cm ² min is introduced. The ratio of benzene vapor to nitrogen is 1:5, and the reaction is stopped after 120 minutes. , cooled down to room temperature in H ₂ atmosphere, collected the product, and the yield of carbon nanotubes was 1.3 g.

Example 7

The induction smelted LNi _3.6 Co _0.4 Fe _0.4 (L is mixed rare earth metal) alloy was crushed to 30 μm-60 μm, and the alloy powder was oxidized in air for 15 minutes to obtain the prepared alloy oxide catalyst sample. Carbon nanotubes were prepared on a fixed-bed gas continuous flow reaction device. Raise the temperature of 120mg catalyst to 823K in a hydrogen atmosphere, and after stabilizing for 20 minutes, turn off the hydrogen, and then pass in a mixture of coal gas and nitrogen at a flow rate of 30ml/cm ² min, the ratio of coal gas to nitrogen is 1:20, The reaction was stopped after 100 minutes, and the temperature was lowered to room temperature in a nitrogen atmosphere, and the product was collected. The yield of carbon nanotubes was 1.9 g.

Example 8

The induction smelted LNi _3.6 Co _0.7 Al _0.3 Mn _0.4 (L is mixed rare earth metal) alloy is crushed to 60 μm-80 μm, and then ball milled for 80 hours to obtain the prepared amorphous alloy sample, the amorphous alloy grain is 50-200 Nano, alloy samples were oxidized in air for 40 minutes to obtain the prepared alloy oxide catalyst samples. Carbon nanotubes were prepared on a fixed-bed gas continuous flow reaction device. Heat 100mg of the catalyst to 823K in a hydrogen atmosphere, and after 20 minutes of stabilization, turn off the hydrogen, and then pass in a mixture of natural gas and nitrogen at a flow rate of 30ml/cm ² min. The ratio of natural gas to nitrogen is 1:8. After 30 minutes of reaction Stop, cool down to room temperature under a nitrogen atmosphere, collect the product, and the yield of carbon nanotubes is 1.7 g.

Claims (6)

1, a kind of preparation method of carbon nanotube is characterized in that it comprises the steps:

(1) is 0.01-200 μ m hydrogen storing alloy powder in air or oxygen under 373-1073K oxidation 2-100 minute with granularity, obtains the hydrogen storage alloy oxidation products;

(2) the hydrogen storage alloy oxidation products with metering places fixed bed gas continuous flow reaction formula device, under 573-1073K hydrogen reducing 5-120 minute;

(3) mixed gas of carbonaceous reactant gases of feeding and carrier gas under 573-1373K; Gas flow rate be the 5-500 milliliter/hour, the ratio of reactant gases and carrier gas is 1/0.1-1/30 in the mixed gas, the reaction times is to get final product in 10-180 minute.The hydrogen reduction product that utilizes is catalyzer, and catalytic pyrolysis prepares carbon nanotube and carbon nano fiber.Carrier gas is hydrogen or argon gas or helium or nitrogen.Under 573-1373K, feed reactant gases or with the mixed gas of carrier gas, gas flow rate be the 5-500 milliliter/hour, the ratio of reactant gases and carrier gas is 1/0.1-1/20 in the mixed gas, the reaction times is 10-180 minute.

2, by the preparation method of the described carbon nanotube of claim 1, it is characterized in that described hydrogen storage alloy can be following composition:

LNi _N-x-y-zCo _xN _yM _z, L is norium, La, Ce, Nd, Pr, Y, N and M are respectively Mn, V, Cr, Al, Fe, Cu, Zn, Sn, Mo, Si, 3≤n≤6,0≤x≤2,0≤y≤2,0≤z≤2;

KNi _A-b-c-dV _bG _cJ _d, K is Zr, Ti, Hf, norium, La, Ce, Nd, Pr, Y, G and J are respectively Co, Mn, Cr, Al, Fe, Cu, Zn, Sn, Mo, Si, 1.2≤a≤3.0,0≤b≤2,0≤c≤2,0≤d≤2;

HN _M-k-jFe _kP _j, H is Zr, Hf, P is Co, Mn, V, Cr, Al, Cu, Zn, Sn, Mo, Si, 0.6≤m≤1.5,0≤k≤1.5,0≤j≤1;

Mg _G-fE _fNi _1-p-qCo _pT _q, E is Ca, Zr, Ti, Hf, norium, La, Ce, Nd, Pr, Y, T is Mn, V, Cr, Al, Fe, Cu, Zn, Sn, Mo, Si, 1.0≤g≤3.0,0≤f≤1.5,0≤p≤1.0,0≤q≤1.0;

Any one or two kinds of above binary or the polynary non-crystaline amorphous metals of perhaps above-mentioned hydrogen storage alloy.

3, by the preparation method of the described carbon nanotube of claim 1, it is characterized in that described hydrogen storage alloy oxidation products is the 1-30% that accounts for carbon nanotube output.

4, by the preparation method of the described carbon nanotube of claim 1, it is characterized in that described carbonaceous reactant gases is hydrocarbon polymer, Sweet natural gas, gas maked coal, liquefied gas, CO or CO ₂

5, by the preparation method of the described carbon nanotube of claim 4, it is characterized in that described hydrocarbon polymer is methane, acetylene, ethene or benzene vapor.

6, by the preparation method of the described carbon nanotube of claim 1, it is characterized in that described carrier gas is hydrogen, argon gas, helium or nitrogen.

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